After originally blaming anti-vaxxers for Mumps outbreaks, CDC backs down and effectively admits MMR vaccine doesn"t work properly, advises adults to take another MMR during Mumps outbreaks, as immunity from the MMR vaccine wanes

In 2017, more than 5,600 people got mumps, the Centers for Disease Control and Prevention says. The year before, in 2016, 6,366 cases were reported. Studies have shown that vaccinating people during a mumps outbreak can help control it. Immunity from the MMR vaccine can wane over time in some people, and the booster dose brings it back up.